# what are the units of interia tensor

Hi there,
What are the units of inertia tensor that we used in AnyBody? Is it kgm2 or m4? Would we need density of material for calculating inertia tensor?
I used pro-engineer software to make some model and imported as stl file in anybody. Now we have to define the mass that we can calculate in pro-e, but how to calculate inertia tensor in pro-e.
In your seated model example (form repository) what units you have followed? because in the main file of seated model example you have define strength muscles as 10,000 ( no units defined) and at the middle of this file strength of shoulder is define as 100 kg/cm2 ? Why is so difference of strength in main file?

Hi ?

The unit for the inertia vector is in kgm^2

The support muscles in the seated human model of 10000 is not used as ordinary muscles. These muscles are artificial muscles that are used for creating unilateral constraints between the chair and the human model, their unit is in N, in general these particular muscles should just be strong enough to avoid that their activation to be too high.

All models in the repository makes use of SI units but in principle you could use any units as long they fit together.

Best regards
Søren

Hi Søren Sir,
If all models in the repository makes use of SI units then why the SpecificMuscleTensionSpine and SpecificMuscleTensionShoulderArm parameters are given in N/cm2 in all examples of repository.
AnyFolder StrengthParameters={
AnyVar SpecificMuscleTensionSpine= 90; //N/cm^2
AnyVar StrengthIndexLeg= 1;
AnyVar SpecificMuscleTensionShoulderArm= 90; //N/cm^2
Regards

Hi

Good point, you are right about these variables

These particular numbers is used for the muscle parameters, basically you can adjust the strength of a limb by increasing this number.

In the muscle strength models this number is multiplied on a PCSA number measured in cm2 so the obtained value is in newton’s. This means that muscle model is still obtaining input values in SI units, and these numbers of for example 90N/cm2 is merely used for converting a PCSA number measured in cm2 to a strength in newtons.

Best regards
Søren